To pursue the aims of this 'Request For Applications" we will assess the utility of Silurana (Xenopus) tropicalis for standard genetic manipulations. To date, a limited number of organisms have been exploited for forward genetic analysis. However, it has become clear that different organisms have different strengths. Our main goal in this proposal is to establish methods that will test the utility of Silurana tropicalis as an additional useful organism for genetic manipulation. A good theoretical rationale has been established, namely that the animal has a relatively short life cycle, and is relatively easy to raise in a lab setting. The embryos develop externally, and in enormous numbers, so are available for screens of early developmental defects. S. tropicalis is a tetrapod, more closely related to humans than is the fish, and therefore more useful for examination of processes such as limb development. By comparison with Xenopus laevis, a pseudotetraploid, S. tropicalis appears not to have undergone either complete or partial genome duplications, so we do not expect multiple genes to have overlapping and therefore redundant functions. In addition, the kinds of embryological experiments that can be done in Xenopus are sufficiently different from those that can be done in the fish, that the use of mutant animals will provide new information about cell and tissue interactions. We will carry out a genetic screen, map deletions cytologically, and optimize insertional mutagenesis.